1. Field of the Invention
The following invention relates generally to video tape reproduction systems, and more particularly to a high speed tape reproduction system in which a plurality of reduced component slave recorders are used in combination with a specially modified high speed reproduction master recorder.
This application is related to copending application Ser. No. 07/095,978 filed Sept. 11, 1987, entitled "System and Method For High Speed Video Tape Reproduction", assigned to the assignee of the present invention.
2. Brief Description of the Prior Art
Prior art video reproduction systems are typically comprised of a master, such as a high quality video tape recorder (player), connected to a multiple number of slave recorders, such as off-the-shelf consumer VHS or BETA video tape recorders, which may be purchased in bulk quantities at great savings. As the master reads the audio and video signals, comprising the recorded program, at the standard playback speed, one or a number of slaves record the information onto blank video tape at the same recording speed. To increase reproduction productivity, as many as 100 slave recorders will be connected to each master recorder. Naturally, the greater the number of slaves combined with each master, the greater the number of tapes produced during each production period.
Combining a large number of slave recorders to each master system can be rather expensive. Apart from the costs associated with purchasing and maintaining as many as 100 slave recorders, the quantity of recorders alone require that adequately sized facilities be available to house the recorders, as well as air conditioning to keep the recorders operable. In addition, each new recording requires the previously recorded tape to be removed and the next blank tape to be installed in each slave recorder. Thus, unless a large number of operators or automated loaders are available, unloading and loading as many as 100 recorders can add a significant amount of time to the overall recording period. In addition, when a large number of operators are utilized, many will have nothing to do while the recording is being made, further adding to the cost of each recording unnecessarily. Thus, prior art recording systems may only be able to record as few as 300 two-hour programs in an eight hour production cycle.
The audio recording industry has long recognized that recording at any rate faster than the standard playback rate will enhance productivity and lower production costs. However, while audio duplicating systems are known to record as fast as 64 times the playback speed, it is much more complicated to increase the speed of video recording. In audio recording, a stationary head records the information onto the tape as the tape is pulled across the surface of the head, at a speed proportional to the signal input rate to the head. If the tape passes across the surface of the head at five times normal speed, the frequency of the input signal must be five times the normal signal frequency. Higher recording signal frequencies are generally achieved by passing the tape across the master playback head at five times normal speed.
In video tape recording, much more is required to increase the recording speed than raising the output signal frequency and proportionally increasing the speed at which the tape passes the head. VHS and BETA tape recorders typically utilize two recording heads mounted 180 degrees out of phase to each other on the circumference of a rotary head drum. The magnetic recording tape is wrapped around a portion of the drum and kept in contact with the circular surface of the drum. When recording, the drum rotates in one direction with respect to the tape so that the two heads move in a wave like motion and produce a series of helical scan recordings on the tape. To increase the recording speed of a prior art recorder, both the longitudinal speed of the tape and rotational speed of the head drum must be increased accordingly.
At 1800 revolution per minute (RPM), the rotational and horizontal movement of the head drum is controllable, however, at double the recording speed, where the head drum rotates at 3600 RPM, and at quadruple the recording speed, where the head drum rotates at 7200 RPM, the rotational movement of the head drum becomes unstable. For each increase in recording speed, there is a square or cube multiplication of technical problems associated with the speed increase. Likewise, for each increase in the rotational speed of the drum, there must be a proportional increase in the video signal frequency. If the playback signal frequency is at 5 MHz, the recording signal frequency of a recording made at four times (4X) speed must be 20 MHz.
Electronics circuits capable of handling high frequency signals are both difficult and expensive to design and build. Where a standard playback speed recording system can be purchased for as little as $500.00, a two times (2X) speed recording system, in order to be cost effective, can cost no more than $1000.00, and a 4X speed recording system can cost no more than $2000.00. A major expense in increasing the overall system recording speed involves the modification of each slave recorder to accommodate high speed recording. Even though the master recorder would require extensive modification, such modification can be carried out fairly inexpensively because only the one master need be modified. However, if the master recorder is modified, each of the 100 or more slaves attached to the master recorder would also require modification. Hence, the costs that could be saved by purchasing a large quantity of consumer VTRs would be forfeited when each VTR was required to be modified.
Although it is possible to operate a standard VTR at 2X speed by increasing the rotational speed of the slave head drum, doing so is not desirable because the standard VTR is not designed to operate at high speeds for extended periods of time. Thus, mechanical constraints on standard VTR's and the probability of reduced equipment life expectancy make converting a standard speed system over to a high speed system impractical.
The use of as many as four heads in the head drum of recorders is well known in the prior art, at least with regard to applications in which the recording speed is the same as the playback speed. Tsuruta, U.S. Pat. No. 4,014,985, issued Sept. 30, 1986, discloses a signal switching system for selectively supplying each of the four recording heads of the head drum with appropriate video signals. Although Tsuruta discloses that a four-head rotary head drum can be used in place of a two-head drum, Tsuruta also discloses that a number of mechanical and electrical conditions must be met for the four-head drum to record a video signal compatible with standard two-head drum recorders. One condition is that the tape must be wrapped around the peripheral surface of the head drum at an angular range of approximately 270 degrees. A second condition is that the tape speed must be selected so that the tape travels by one track pitch during one field period in which one rotary video head rotates by 270 degrees.
In order to meet the above conditions, Tsuruta disclosed that the diameter of the head drum must be reduced to 2/3 the diameter of a standard two-head drum and that an elaborate head signal switching system must be employed, rather than the standard practice of applying continuous recording current to the two recording heads. Thus, recording current is supplied to one head as it makes a 270 degree rotational pass, while the two immediately following heads are supplied no recording current, then recording current is supplied to the third immediatly following head, etc. A signal switching system that provides accurate phase control synchronization for a reduced diameter four-head drum similar to that disclosed in Tsuruta is disclosed in U.S. Pat. No. 4,609,952, issued Sept. 2, 1986, to Yoshino et al.
Other increased speed recording systems, utilizing a variety of recording techniques, have been developed over the years to overcome the problems associated with increasing tape and head drum speeds. One such system is disclosed by U.S. Pat. No. 4,320,486, issued Mar. 16, 1982, to Cooley et al., in which an optical storage medium is used as an intermediate transfer medium from which recorded information signals may be reproduced at speeds of 2 to 200 times normal playback speed. However, as with all such system before, such high speed recording systems have greater application to audio recording, where the heads are stationary, then to video recording, where heads must be rotated faster to accommodate the increased signal frequency supplied to the slave recorder. SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a system for producing a high quantity of compatible video recordings at a speed which is some multiple of the playback speed of each recording.
Another object of the present invention is to provide a reduced component slave recorder capable of operating at a greater than standard playback speed.
Still another object of the present invention is to provide a high speed video reproduction system which can use either a plurality of reduced component VTR slave recorders or reduced component pancake recorders.
A further object of the present invention to provide a high-speed master recorder that is capable of reproducing a video recording and developing a corresponding output signal which may be directly applied to the write heads of a plurality of slave recorders.
A still further object of the present invention is to provide a high speed slave recorder that is not simply operated faster than its standard operating speed in order to decrease the standard recording time.
A still further object of the present invention is to provide a magnetic tape recording system in which multiple read heads supply recording signals to multiple write head pairs.
Briefly, a preferred embodiment of the present invention utilizes a master recorder, including an optical disc player having two read heads located on opposite sides of the master recording disc for scanning the individual tracks of the disc and developing electrical signals representing the data stored. Also included within the master recorder is a timing means for coordinating the output sequence of the developed signals from the master recorder, and a processing means for configuring the developed signals so that they may be recorded onto a video tape by each of the slave recorders. The master recorder is connected to a plurality of slave recorders, including a head drum, having four write heads located at 90 degree angles to each other around the circumference of the head drum whereby oppositely located heads form a electrically connected head pair, and mechanical and electrical components for moving and controlling the head drum and tape.
These and other objects and advantages of the present invention will become apparent to those skilled in the art after having read the following detailed description of the preferred embodiment illustrated in the several figures of the drawing.